Ingot heating furnace



Dec.16,1969 GENTRY HAL 3,484,086

INGOT HEAT ING FURNACE Filed July 29, 1968 4 Sheets-Sheet 2 INVENTOR Dec. 16, 1969 c, GENTRY ET AL 3,484,086

INGOT HEATING FURNACE Filed July 29, 1968 4 Sheets-Sheet 3 INVENTORS 63442455 5. wafer ewer/fi. (swam/M miufs United States Patent INGOT HEATING FURYACE (.harles B. Gentry and Robert M. Scanlon, Grand Rapids, Mich., assignors to Granco Equipment, Inc., Grand Rapids, Mich, a corporation of Delaware Filed July 29, 1968, Ser. No. 748,391 Int. Cl. F27b 9/24 US. Cl. 263-45 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to an ingot heating furnace in which metal ingots such as aluminum are heated to elevated temperatures by direct impingement of the heating flame. The ingots are conveyed through a furnace having a plurality of heating zones, each one containing a burner pattern which is particularly adapted to the size ingot being heated. Different size ingots can be processed serially by the furnace by programming the burner pattern for the ingot size so that the flames do not over fire the ingot. The burner nozzles protrude out from the sides of the furnace to eliminate howling.

This invention relates to metal heating. In one of its aspects it relates to an ingot heating furnace having a furnace chamber with a plurality of article heating zones, each zone having a plurality of burners in the side walls. The burners in each zone are arranged in a manner so as to heat the ingots individually in each zone, by impinging a flame on the ingots as they are carried intermittently through the furnace.

In another of its aspects, the invention relates to a furnace construction adapted for heating different size ingots comprising a burner array which can be programmed according to the size and shape of the ingot.

In still another of its aspects, the invention relates to an ingot heating furnace having horizontal and vertical rows of heating burners wherein the centrally disposed burners have a capacity greater than that of the outer of the burners.

In still another of its aspects, the invention relates to a method for heating metal ingots by direct flame impingement on the ingots as they pass through the heating zone.

Conventionally, large ingots such as aluminum and steel are heated in large soaking pits to an elevated temperature suitable for hot rolling into thin gauge material. Many of the ingots must remain in the soaking pits for an extended period of time in order to homogenize the composition of the ingots. Other ingots do not require a soak and can be processed as soon as they reach the proper temperature.

The soaking pits employ convection and radiation to heat the ingots. The heating of the ingots in this manner is quite time consuming, generally taking about 18 to 24 hours.

I have now discovered an improved furnace for rapidly heating ingots, which furnace can heat the ingots to an elevated temperature suitable for rolling in a relatively short period of time. This furnace employs a flame impingement process in which the heating flame strikes and envelops on the article being heated. With the use of the invention, even ingots which have to be soaked can be prepared for rolling.

By various aspects of this invention, one or more of the following, or other, objects can be obtained.

It is an object of this invention to provide a method and apparatus for rapidly heating metal ingots.

It is a further object of this invention to provide a method and apparatus for heating different size ingots simultaneously.

It is a further object of this invention to heat metal ingots by direct flame impingement in which heating, melting at the edges and corners of the ingot is prevented.

Other aspects, objects, and the several advantages of this invention are apparent to one skilled in the art from a study of this disclosure, the drawings, and the appended claims.

According to the invention, there is provided an article heating furnace used generally for large metal ingots such as steel and aluminum. The furnace preferably has a plurality of spaced areas of high heat intensity, each area having independent heat controlling means. The ingots are heated by an array of burners in the side walls in each area of high heat intensity. The burners preferably project slightly out from the side of the wall and direct a flame against the sides of the ingot. Means are provided to control the supply of fuel to burners such that the burner pattern approximates the shape of the ingots within a given area of high heat intensity.

The ingots are conveyed through the furnace on a con tinuous conveyor having I-shaped, ingot supporting means. The ingots are so supported on the conveyor that all ingots, regardless of size, are positioned in front of an area of high heat intensity. Preferably, the ingots are centered in each area.

Preferably, at least a portion of the centrally disposed burners have high capacity and a portion of the outer burners in each zone have low capacity.

The invention will now be described with reference to the accompanying drawings in which:

FIG. 1 is a side elevational sectional view of a furnace embodying the invention;

FIG. 2 is an end view of the furnace shown in FIG. 1, seen along lines II of FIG. 2;

FIG. 3 is a side elevational view of the burner pattern in each zone in the furnace, generally seen along lines III-III of FIG. 2; and

FIG. 4 is a schematic representation of a control system for one side of a single heating zone within the furnace.

Referring now to the drawings, a heating furnace 2 is provided having spaced heat zones 4, 6, and 8 of high heat intensity. The heating furnace 2 has a refractory roof 10, side walls 12 and 14, and a floor 16 formed from a pair of inwardly directed refractory members, leaving a narrow slot in the central portion thereof. A housing 18 surrounds and is spaced from the refractory walls of the heating furnace. The housing 18 has side walls 20 and top 22. A plurality of exhaust openings 24 are provided in the refractory roof 10 for drawing out hot exhaust gases. The exhaust gases are drawn by a fan 27 through an exhaust conduit 26. The side walls 20 of the exterior housing are supported by members 21 which permit the fan to draw air in beneath the side walls 20.

Ingots 28, 30, and 32 are supported on a conveyor system 34 in heating zones 4, 6, and 8 respectively. The ingots have a thin dimension (as seen from FIG. 2), which dimension is perpendicular to the direction of movement of the ingots through the furnace. The ingots have a pair of rectangular sides which are parallel to the direction of movement of the ingots through the furnace.

The ingots are supported and moved through the furnace by a conveyor system 34 comprising ingot carriers 36 driven by chain 44 on sprocket wheels 52 and 54. The chain 44 is intermittently driven by motor 55. The ingot carriers 36 are generally I-shaped as seen in FIG. 2 so that the narrowest portion of the carrier can fit within the narrow slot formed by the inwardly directed refractory floor member 16. Each ingot carrier 36 is fixed to a car 38 which has wheels 40 rotatably attached thereto. Rails 42, supported by support member 46 and cross support 48, guide and support the rollers 40. A lower rail 42a is provided for supporting the ingot carriers 46 on their return trip. The lower rails 42a are supported by lower rail supports 50.

As seen in FIG. 2, the return of the conveyor belt is excavated beneath the floor level. A receiving platform 56 is provided for receiving the heated ingots as they pass from the furnace. Other means can be provided for removing the heated ingots from the conveyor means. For example. the conveyor means 34 could extend out from the end of the furnace and the ingots could be picked up from the conveyor by an overhead crane.

The ingots are heated by flames from an array of burn ers in each side wall in each area of high heat intensity. Generally the burner array generally conforms to the configuration of the largest ingot to be processed by the furnace. In order to prevent over heating of smaller ingots, the fuel supplied to the burner pattern is controlled such that the flame pattern conforms with at least one dimension of the configuration of the ingot as projected onto the side walls of the furnace chamber, Preferably, the fuel supply is controlled so that the flame pattern generally conforms to the general configuration of the ingots as projected onto the side Walls of the furnace.

The ingots are heated by flames which, due to the velocity of the combustible fuel through the burners, substantially envelop the ingot. The burners are so spaced from the ingot side walls and the velocity of the combustible fuel through the burners is such that the reducing portion of the flame contacts the surface and envelops the ingot. In this manner, oxidation of the surface of the ingot is minimized and substantially eliminated. In some instances, the scale formation on the ingots such as steel, can actually be reduced.

Referring now specifically to FIG. 3, the flame is projected onto the billets from horizontal rows of burners 60, 62, 64, 66, 68, and 70, and each row of burners comprises a plurality of individual burner tiles, each burner tile projecting slightly out from the wall (see FIG. 2). The projection of the burners from the Wall of the furnace reduces howling within the furnace. Howling is generally the term used to designate a loud noise generated by the turbulent flow of gases through a constricted space. It has been found that the projection of the burners from the furnace wall substantially eliminates this problem of howling.

As can be seen from FIG. 1, the furnace must be adapted to accommodate different size billets. In general, the billet sizes can range from for example, x x 80 inches to a maximum of 18 /2 x 60 x 144 inches. The different extremes of ingot sizes as projected onto the side Wall are shown in phantom lines in FIG. 3. According to the invention, the furnace is adapted to heat different size ingots simultaneously. To this end, each row of burners is horizontally manifolded, i.e., there is a single manifold for each row of horizontal burners within each zone.

Referring to FIG. 4, in each high intensity area, there would be a manifold 72 for burner row 60, a manifold 74 for burner row 62, a manifold 76 for burner row 64, a manifold 78 for burner row 66, a manifold 80 for burner row 68, and a manifold 82 for burner row 70. According to one embodiment of the invention, over heating of the ingots is prevented by programming the burner pattern to correspond with the general configuration of the ingot in the particular zone. To this end, a fuel conduit 84 having branch conduits 86, 88, 90, 92, 94, and 96 is provided for supplying fuel to manifolds 72, 74, 76, 78, 80, and 82. An air supply conduit 98 is provided to mix the proper amount of air with the fuel. It is to be understood that the system shown in FIG. 4 is schematic. Other systems for mixing fuel and air can also be employed. For example, the fuel and air can be passed through separate pipes to different areas of each burner tile. Control valves 112, 114, and 116 are provided in conduits 86, 88, and 90 respectively. According to the invention, the flow of combustible fluid to one or more of manifolds 72, 74, and 76 can be independently controlled by a controller 118 to regulate the burner pattern in accordance with the size of the ingot within the zone. For example, if ingot 30 were in the zone, all of the manifolds would be operating. If ingot 28 were in the zone, the valves 112 and 114 would be closed and therefore no flame would be emanating from the burner rows 60, 62, and 64 Inthis manner, the burners do not over fire the ingots and the flame pattern would conform to one dimension (i.e., height) of the ingot as projected onto the side Wall.

As a further refinement, the conduits supplying the end burner tiles 62a have valves 100. The conduits supplying end tiles 64a have valves 102. Each of these valves has a control line connected to controller 118 for controlling the operation of the valve and hence the flow of fuel to these burners. The controller can be so pro grammed to close valves 100 when the valve 112 closes off the flow of fuel to manifold 72. Valves 102 can be programmed to close when valve 112 and/or valve 114 closes. Various combinations of valve control programs can be devised so that the burner pattern generally conforms to the ingot configuration as projected onto the side wall of the high heat intensity area. For this purpose, a plant can have a plurality of programs, each conforming to a standard ingot size for the particular plant.

Further according to the invention, the heating capacity of the burners within each row are selected to prevent over heating of the ends and corners of the ingot. As used herein, burner capacity means the heat producing ability of the burner at maximum output. Referring now to FIG, 3, the burners in burner row 60 comprises a plurality of medium capacity burners 60a. The burners in burner row 62 comprise medium capacity burners 62a at the ends of the rows, low capacity bumers 62b near the ends of the rows, and medium capacity burners 620 in the central portions of the rows.

Burner row 64 has burners 64a of medium capacity. Burner row 66 has outer burners 66a of medium capacity, and centrally located burners 66b of high capacity. Burner row 68 has no end burners extending to the outer portion of the zone, Inner burners 68b of row 68 are of medium capacity. Burner row 70 has outer burners 70a of low capacity and inner burners 70b of medium capacity.

By this arrangement, over heating of the corners of the ingots is prevented. When a smaller ingot is being heated, top row 60 and end burners 62a can be cut off from fuel in a manner which has been hereinbefore described. If burners 62b fire laterally of the side walls of the ingot there will be no over heating of the top corners of the ingot since burners 62b are of low heating capacity. It has been found that the centrally disposed rows can laterally over fire without over heating problems. Thus, rows 64 and 66 can laterally over fire if desired without over heating the edges. The bottom corners of the ingot are the most susceptible to over heating. To overcome this problem, the second row of burners is only as long as the shortest ingot. The bottom row of burners has end burners 70a of reduced capacity. These burners although always on, will not cause over heating due to the fact that a certain amount of heat is lost through the bottom slot of the furnace.

Control valve 126 is provided in fuel conduit 84 for adjusting the amount of fuel supplied to each high heat intensity area. The fuel is preferably controlled according to a thermocouple fixed to a thermocouple actuating means 122. The thermocouple actuating means 122 causes the thermocouple probes 121 to move into the furnace to contact the billets and out from the furnace to cool. The total amount of heat supplied to each zone is accordingly controlled depending on the temperature of the billets as sensed by the thermocouple probes 121. To this end, a temperature recorder controller 124 is provided.

In operation, the temperature of each billet is sensed by the thermocouple probes 120. The signal generated by the thermocouple probes 120 is transferred to temperature recorder controller 124, which in turn, controls flow controller 125 to operate valve 126. In this manner, the total amount of fuel supplied to each high heat intensity area or zone can be regulated to maintain a predetermined ingot temperature. For example, if the billet in the area has reached the desired temperature, as measured by the thermocouple 120, the temperature recorder controller 124 will signal the flow controller 125 to adjust the valve 126 to decrease the total amount of fuel supplied to the burners in that area or zone. With this construction, the furnace can be made to idle in the event that a shutdown on the roller mills is required. This control system prevents over heating of the billets during this idling time. Further, the control system permits flexibility of the furnace. For example, it hot ingots are positioned within the furnace, less fuel is required to heat them to the desired temperature. The temperature sensing and control mechanism will permit the furnace to heat these billets to the proper temperature without over heating. On the other hand, if cold ingots are put into the furnace, the heat required to raise the ingots to the proper temperature will be greater. Accordingly, the temperature sensed by the thermocouples 120 will cause more fuel and air to be supplied in order to heat the ingot.

The use of multiple heating zones in heating the ingots permit different size ingots to be raised to the proper temperature by degrees. The furnace can have more or less than three heating zones.

Further, by the use of the invention, different size ingots can be heated without altering the furnace construction. For example, each high heat intensity area or zone can be programmed for accommodating standard plant sizes. In this manner, the burner pattern in each area or heating zone is then set for a particular ingot which is positioned within that heating zone. This can be done by a selector switch and appropriate controls to the individual burners.

With the use of the invention, alloy ingots which must be soaked for homogenization can be heated and held at the homogenization temperature for the required homogenization time. In this manner, the alloys can be rolled after they are removed from the heating furnace without the use of a soaking pit.

Reasonable variation and modification are possible within the scope of the foregoing disclosure and drawings of the invention without departing from the spirit thereof.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

We claim:

1. An apparatus for heating articles comprising:

a furnace chamber having an entrance and an exit opening and formed by a roof and oppositely disposed side walls, said side walls forming a channel for the passage of articles therebetween;

a plurality of spaced areas of high heat intensity along said channel in said side walls between said entrance and exit, each of said areas comprising a plurality of rows of burners in each side wall in opposing relationship to each other, said burners forming a rectangular configuration whose dimensions are substantially greater than the distance between said side walls;

conveyor means within said furnace chamber between said entrance and exit for intermittently moving said articles through said areas of high heat intensity, said conveyor means including positioning means for supporting one of said articles in each area of high heat intensity between said oppositely disposed rectangular configuration of burners such that the bottom portion of said articles is directly in line with the lowermost row of burners in said rectangular configuration; means for supplying fuel to said burners in each high heat intensity area at such velocity that the totality of said burners in each said area of high heatintensity emits a flame which substantially completely envelops said article Within said area; and

gas withdrawal means in an upper portion of said furnace chamber to withdraw the products of combustion from each of said areas of high heat intensity so as to maintain independent control of the temperature in each of said areas of high heat intensity.

2. An apparatus according to claim 1 wherein there is provided a floor in said furnace having a narrow slot, said conveyor means comprises a plurality of I-shaped members with the narrow portion of said I-shaped members in said slot, the top portion of said I-shaped members supporting said articles, means are provided to move said I-shaped member through said furnace in said narrow slot whereby said articles are conveyed through said furnace and the heat lost through said furnace floor is minimized.

3. An apparatus according to claim 1 wherein means are provided in each high heat intensity area to control the fiow of fuel to said burners so that the flame producing burner pattern in each area approximates the shape of the article in each high heat intensity area whereby over heating of the edges of the articles is avoided.

4. A furnace construction adapted for heating different sized articles, such as ingots, without overheating the corners of the articles, the construction comprising:

oppositely disposed side walls;

a plurality of horizontal rows of burners in each side wall in opposing relationship to each other, said burners forming a rectangular configuration whose dimensions are substantially greater than the distance between said side walls;

means for withdrawing combustion products from an upper portion of said furnace;

means for supply fuel to said burners at such velocity that the totality of said burners emits a flame which substantially completely envelops an article whose shape lies within the confines of the rectangular pattern;

said fuel supply means including a common manifold supplying fuel to a top row of burners in said rectangular configuration;

means for supporting an article between said side walls such that the lowermost portion of said article is directly in line with a bottom row of burners in said rectangular configuration; and

independent control means to regulate the amount of said fuel to said common manifold whereby articles of different size can be heated without overheating the corners of said articles.

5. A furnace construction according to claim 4 wherein central most burners in said rectangular pattern are provided with burner capacity at maximum output greater than that of said other burners.

6. A furnace construction according to claim 4 wherein said burners extend out from said side walls to prevent howling within the walls of said furnace.

7. A furnace construction for heating metal ingots and the like comprising: side walls and a top wall; a plurality of rows of burners in each of said side walls in opposing relationship to each other, said burners forming a rectangular configuration whose dimensions are substantially greater than the distance between said side walls; means for supplying fuel to said burners at such a velocity that the totality of said burners emits a flame which substantially completely envelops an article between said side walls; the centrally disposed burners in said rectangular configuration having a burner capacity at maximum burner output greater than that of the outer of said burners in said rectangular con-figuration such that the heat producing flame from said centrally disposed burners is greater than the heat producing flame from burners at the outer portion of said rectangular configuration, whereby said article between said side walls is heated rapidly and evenly without overheating the edges and corners thereof.

8. A method for heating metal ingots by direct flame impingement comprising: intermittently passing said ingots through a plurality of heating zones, contacting said ingots in each heating zone with a flame for heating the same, said flame enveloping substantially the entire surface of said ingot with a reducing portion of said flame, and controlling the flow of fuel to each heating zone such that the flame pattern of each heating zone generally conforms to the shape of each ingot within each of said zones.

9. A furnace construction adapted for heating different size articles, such as metal ingots, without overheating the corners of the articles, the construction comprising:

oppositely disposed side walls;

a plurality of rows of burners in each of said side walls in opposing relationship to each other, said burners forming a rectangular configuration whose dimensions are substantially greater than the distance between said side walls;

means for positioning an article between said side walls such that the lowermost portion of said article is directly in line with the lowermost row of said burners in each burner configuration;

means to supply fuel to each of said burners at such a velocity that the totality of said burners emits a flame which substantially completely envelops said articles with said flame;

gas withdrawal means at an upper portion of said side walls to withdraw the products of combustion from said furnace; and

means for controlling the flow of fuel through said fuel supply means to said burners such that the flame pattern in each array of burners generally conforms to at least one dimension of the configuration of said article as projected onto said side walls whereby overheating of the corners of said article is avoided.

10. A furnace construction according to claim 9 wherein said control means includes means for controlling the flow of fuel to said burners such that the flame pattern generally conforms to the configuration of said article as projected onto said side walls.

References Cited UNITED STATES PATENTS 1,205,503 11/1916 Barnhart et al. 263-8 2,142,824 1/1939 Olson et a1 2636 2,504,707 4/1950 Lloyd 26328 X 2,539,135 1/1951 Hess 2638 3,386,717 6/1968 Foster et a1. 26328 FOREIGN PATENTS 834,332 11/1938 France.

JOHN J. CAMBY, Primary Examiner U.S. Cl. X.R. 26328 

